• Journal of Mechanical Science and Technology
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• v.14 no.2
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• pp.226-235
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• 2000

The performance prediction of an airfoil fan using a commerical code, STAR/CD, is verified by comparing the calculated results with measured performance data and velocity fields of an airfoil fan. The effects of inlet tip clearance on performance are investigated. The calculations overestimate the pressure rise performance by about 10-25 percent. However, the performance reduction due to tip clearance is well predicted by numerical simulations. Main source of performance decrease is not only the slip factor but also impeller efficiency. The reduction in performance is 12-16 percent for 1 percent gap of the diameter. The calculated reductions in impeller efficiency and slip factor are also linearly proportional to the gap size. The span-wise distributions of phase averaged velocity and pressure at the impeller exit are strongly influenced by the radial gap size. The radial component of velocity and the flow angle increase over the passsage as the gap increases. The slip factor decreases and the loss increases with the gap size. The high velocity of leakage jet affects the impeller inlet and passage flows. With a larger clearance, the main stream moves to the impeller hub side and high loss region extends from the shroud to the hub.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.202-208
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• 2003

This study carried out a cutting experiment on Duralumin A16061-76, which is light but strong and highly anticorrosive, so recently popular as a lightweight material, by changing cutting conditions and alternating 4 insert tips, and examined the effect of each insert tip on cutting force at certain cutting conditions, the measurements of the coarseness of processed surfaces roughness, and the chip workability. The 1311owing conclusions were drawn from the results. Cutting force for cutting tool is when insert tips were alternated at each cutting condition, the cutting force of cutting tools was highest then CBN tools were use(1 next by Ceramic tools, Cermet tools, and WC tools. Therefore, WC tools are considered most suitable for cutting Duralumin A16061-T6. Surface roughness as for the coarseness of surfaces according to insert tips applied to Duralumin A16061-T6 under the cutting condition of depth of cut below 1mm, feed rate below 0.24mm/rev and cutting speed over 100m/min the coarseness of material surface roghness appeared to be finest when WC tools were used, next by Ceramic tools, Cermet tools, and CBN tools.

• Journal of the Korean Society of Tobacco Science
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• v.4 no.1
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• pp.29-35
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• 1982

Potassium deficiency symptoms were studied with flue-cured tobacco which was applied with different levels of compound fertilizer (10-15-20) ; 75kg, 100hg, and 125kg/10a. Ratio of N/$K_2O$ in leaves was increased from bottom to top stalk position due to the increase of nitrogen content in leaves. Nitrogen content in leaves was increased from stalk to tip as wall as from midrib to laminae, but vice versa in potassium content. Consequently, resulting in potassium deficiency symptoms in tip of leaves. Rate of reabsorption by rainfall during the latter part of growth was highest at top stalk position in case of nitrogen, but lowest in potassium. This observation was more evident with higher application rate of fertilizer. Nitrogen content of about 4 % in leaves of top stalk position applied with 125kg/10a was maintained up to 85days after trans planting. No increase in potassium in upper leaves was observed over the level of 100kg/10a fertilizer application. As the result, N/$K_2O$ ratio in leaves of top stalk position applied with 125kg/10a was kept at more than 1.0 up to 85days after transplanting, but it was less than 0.9 at 65days after tracts planting with less than 100kg/10a fertilizer application.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.168-173
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• 1998

A numerical analysis of axisymetric backward facing step main nozzle flow in air jet loom has been accomplished. To obtain basic design data for an optimum main nozzle for an air-jet loom and to predict the transonic/supersonic flow, a characteristic based upwind flux difference splitting compressible Navier-Stokes method has been used. The wall static pressure of the main nozzle and the flow velocity changes in the nozzle tube were analyzed by changing air tank pressures and acceleration tube lengths. The flow inside the nozzle experiences double choking one at the needle tip and the other at the acceleration tube exit at tank pressures over $4kg_f/cm^2$. The tank pressure $P_t$ leading to the critical condition depends on the acceleration tube length; i.e, $P_t$ is higher for longer acceleration tubes. The $P_t$ value required to bring the acceleration tube exit to the critical condition is nearly constant regardless of acceleration tube length. The round needle tip shape might lead to less total pressure loss when compared with step shape.

• The Korean Journal of Pain
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• v.9 no.1
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• pp.183-186
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• 1996

When medical therapy fail to relieve pain at tolerable level for patients confirmed with trigeminal neuralgia, presence of mass lesion excluded, surgery is indicated. Innumerable surgical strategies have been attempted for the treatment of trigeminal neuralgia but only four have proven appropriate: (1)stereotactic radiofrequency gasserian ganglionotomy, (2) percutaneous glycerol gangliolysis, (3) percutaneous microcompression, (4) microvascular decompression. Radiofrequency thermocoagulation of the gasserian ganglion stems from the efforts of Sweet. This technique is the surgical treatment of choice around the world for surgical treatment for trigeminal neuralgia. Since 1986, over 14,000 cases have been reported utilizing this technique. To improve the treatment method further, an electrode with a flexible curved tip has been developed for easier and more precise electrode placement and lesion production during the thermocoagulation of gasserian ganglion. This operation was performed recently on three patients at Hallym University Hospital. using a curved tip electrode. Complete relief of pain was achieved for all patient. However, some complications were noted.

• International Journal of Concrete Structures and Materials
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• v.11 no.2
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• pp.365-375
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• 2017

An experimental evaluation of crack propagation and post-cracking behavior in steel fiber reinforced concrete (SFRC) beams, using full-field displacements obtained from the digital image correlation technique is presented. Surface displacements and strains during the fracture test of notched SFRC beams with volume fractions ($V_f$) of steel fibers equal to 0.5 and 0.75% are analyzed. An analysis procedure for determining the crack opening width over the depth of the beam during crack propagation in the flexure test is presented. The crack opening width is established as a function of the crack tip opening displacement and the residual flexural strength of SFRC beams. The softening in the post-peak load response is associated with the rapid surface crack propagation for small increases in crack tip opening displacement. The load recovery in the flexural response of SFRC is associated with a hinge-type behavior in the beam. For the stress gradient produced by flexure, the hinge is established before load recovery is initiated. The resistance provided by the fibers to the opening of the hinge produces the load recovery in the flexural response.

• Journal of Plant Biology
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• v.27 no.3
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• pp.139-147
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• 1984

This in vitro study was employed to clarify the effects of several pollutants i.e. $SO_2$, fluoride, cadmium(Cd), aluminum(Al) and NaCl, on the organogenesis and growth responses of shoot-tip, stem and multiple-buds segments derived from hypocotyl or cotyledon culture of petunia seedlings. ${Na_2}{SO_3}$levels of more than 200$\mu{g}$/ml had significantly reduced organogenesis, growth, and chlorophyll content. The injuries caused by ${Na_2}{SO_3}$, concentration of more than 400$\mu{g}$/ml were alleviated by increasing hydrogenion concentration of medium, indicating some relationship between two factors. Organogenesis was not affected by the fluoride concentration up to 100ppm in the media, but the growth and chlorophyll content were greatly reduced by the fluoride. The effect of Cd depended on the explant sources used for the culture; 1.0ppm was effective for fresh weight increase in shoot tip culture, and 3.0ppm in stem segments culture. Organogenesis and growth were greatly reduced by more than 10.0 Cd treatment. Growth and formation of shoots were better with Na conc. of 0.3% compared to control, but those of roots were inhibited. Na concentration goes over 1.0%, organogenesis and subsequent growth were inhibited, and chlorophyll synthesis was drastically reduced. Chlorophyll content was increased on the medium supplemented with Al 50$\mu{g}$/ml compared to control. However the formation and growth of shoots were greatly inhibited with more than 400$\mu{g}$/ml and roots were not produced at all.

• Journal of the Korean Society of Safety
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• v.18 no.4
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• pp.51-56
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• 2003

The goal of this study is to show the way to decrease the noise from air nozzles. The variables of this test are the shapes of air nozzles, air flow rate and the distance between a reflection plate and a nozzle tip. This experiment is aimed to find the most appropriate condition to minimize the noise. These are the results. If diameter ratio is more than 12:8, noise level increases by over 10 dB(A) regradless of the distance between a reflection plate and a nozzle and the existence of a reflection plate. And when $L_2$ of a nozzle is 5mm long, noise level rise relatively highly. So, it is strongly recommended that $L_2$ should be manufactured more than 10mm. The reason for a high intensity noise is that when diameter ratio is more than 12:8, the diameter of a nozzle tip($D_2$) turns small drastically, which increases the air velocity. It is assumed that when the vortes is great around the spots where a nozzle hole is suddenly smaller, great turbulent flow increases much noise.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.397-400
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• 2011

MDO Optimization for a low pressure axial compressor rotor has been carried out to improve aerodynamic performance and structural stability. Global optimized solution was obtained from an artificial neural network model with genetic algorithm. Optimized rotor model has a high blade loading near hub and near zero incidence flow angle near tip region to reduce the incidence loss and flow separation at trailing edge region. Also the rotor shape is converged to a trapezoid shape to reduce the maximum stress occurred at the root of the blade. Numerical simulation results show that rotor has 87.6% rotor efficiency and safety factor over than 3.

• Clinics in Shoulder and Elbow
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• v.22 no.1
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• pp.37-39
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• 2019

Irreducible dislocation of the elbow is an uncommon event. We present the case of a posterolateral elbow dislocation after a fall injury in a 67-year-old woman. A closed reduction performed in the emergency department was unsuccessful since the limited passive range of motion resulted in difficulty to perform longitudinal traction and flexion. Computed tomography images showed that the posterolateral aspect of the capitellum was impacted by the tip of the coronoid process, thus appearing similar to the Hill-Sachs lesion in the humeral head. Subsequent open reduction of the elbow revealed the dislocation to be irreducible since the tip of the coronoid process had wedged into a triangular Hill-Sachs-like lesion in the capitellum. The joint was reduced by providing distal traction on the forearm, and main fragments were disengaged using digital pressure. At the 3-month follow-up, the patient reported no dislocations, and had an acceptable range of motion. Thus, we propose that to avoid iatrogenic injury to the joint or other nearby structures, irreducible dislocations should not be subjected to repeated manipulation.